1. Field of the Invention
The present invention relates, in general, to a method for producing a titanium silicide in a semiconductor device and, more particularly, to a reactive physical deposition method by which a titanium silicide of low specific resistance can be obtained with a significant improvement in productivity and a significant reduction in production cost.
2. Description of the Prior Art
The high integration of semiconductor devices requires conductive wirings to be of low resistance. In the case that a polysilicon layer acts as a word line, the resistance of the word line increases with its length, leading to a decrease in operation speed and an increase in power consumption.
In order to reduce the resistance of such a word line, conventionally, a physical deposition method was performed to deposit titanium, followed by a thermal treatment to form a titanium silicide. If the titanium is too thin, the resulting titanium silicides are highly apt to aggregate each other so that not only is their surface morphology degraded but also a uniform deposition on a substrate is not accomplished. On the other hand, if the titanium is too thickly deposited, surplus Ti after the formation of titanium silicide causes junction leakage. Thus, the titanium should be deposited to an optimal thickness but this is very difficult owing to the unreliable reproductivity of conventional processes. In fact, the physical deposition method is now almost never employed.
In chemical deposition methods, a titanium source and a silicon source are used at the same time to deposit a titanium silicide. Since the titanium source reacts mainly with silicon, the substrate, it is consumed too much. In addition, the chemical deposition methods have another significant problem of being low in process reproductivity.